This invention relates to an event rate counter for measuring the number of events occurring per unit of time having automatic switching so that the order of a multiply-divide scaling sequence for high frequency pulse trains is the reverse of the sequence order for low frequency pulse trains.
Event rate counters in the form of digital tachometers have been known in which a pulse train is derived from a rotating gear having N teeth, the frequency of which is scaled to provide a direct reading in revolutions-per-minute. However, the dynamic frequency range of such tachometers is limited by the order in which scaling by multiplication and division occurs. Further problems arise from ineffective noise discrimination of the input sensor signal resulting in erroneous speed indications.